Generally, a wiper arm includes an arm head secured to a vehicle, a retainer capable of retaining a blade for wiping a windshield, and a bearing device for pivotably attaching the retainer to the arm head. The arm head has a bolt receiving hole provided at one end thereof so that the arm head can be secured to the vehicle body with a bolt inserted through the bolt receiving hole. The arm head further has a hinge portion at the other end thereof, which is opposite to the one end.
The bearing device includes an outer bushing press-fitted into the hinge portion of the arm head, an inner bushing rotatably inserted into a bore in the outer bushing, and a rivet inserted into a bore in the inner bushing to secure the retainer and the inner bushing together integrally. Thus, a hinge portion of the retainer, the inner bushing, and the rivet are pivotable relative to the hinge portion of the arm head and the outer bushing.
The arm head is, generally, formed of aluminum with a view to achieving a weight reduction. On the other hand, the outer bushing, which is press-fitted into the hinge portion of the arm head, needs to have mechanical strength sufficient for supporting the retainer, the inner bushing, and the rivet. To ensure such strong mechanical strength, the outer bushing is, generally, formed of stainless steel.